Optical frequency domain imaging (“OFDI”), which may also be known as swept source optical coherence tomography (“OCT”), is a technique associated with OCT concepts that generally uses a wavelength-swept light source to probe the amplitude and phase of back scattering light from tissue. Exemplary OFDI techniques and systems are described in International Application No. PCT/US04/029148. Method and system to determine polarization properties of tissue is described in International Application No. PCT/US05/039374. The OFDI technique can offer intrinsic signal-to-noise ratio (“SNR”) advantage over the time-domain techniques because the interference signal can be effectively integrated through a Fourier transform. With the recently developed rapidly tunable lasers in the 1300-nm range, the OFDI technique has enabled significant improvements in, e.g., imaging speed, sensitivity, and ranging depth over the conventional time-domain OCT systems. For example, such OFDI procedures/techniques can be used for imaging skin, coronary artery, esophagus, and anterior eye segments.
While retinal imaging is an established clinical use of the OCT techniques, this application has not been implemented using the OFDI procedures because the optical absorption in the human eye at 1300 nm may be too large. The standard spectral range of the conventional ophthalmic OCT techniques has been between 800 nm and 900 nm where the humors in the eye are transparent and broadband super-luminescent-diode (“SLD”) light sources are readily available. It has been has suggested that the 1040-nm spectral range can be a viable alternative operating window for a retinal imaging, and can potentially offer a deeper penetration into the choroidal layers below the highly absorbing and scattering retinal pigment epithelium. The spectral domain (“SD”) OCT systems, also known as Fourier domain OCT systems, that use broadband light sources at 800 nm and arrayed spectrometers have been provided to facilitate a three-dimensional retinal imaging in vivo with a superior image acquisition speed and a sensitivity to conventional time-domain OCT techniques.
As compared to the SD-OCT techniques, the OFDI procedures offer several advantages, such as an immunity to motion-induced signal fading, simple polarization-sensitive or diversity scheme, and long ranging depth. However, a clinical-viable OFDI system for imaging posterior eye segments has previously been unavailable, primarily due to the lack of a wide-tuning rapidly-swept light source in a low water absorption window. Indeed, despite the widespread use of the conventional OCT for retinal disease diagnostics, imaging posterior eye segment with OFDI has not been possible.
Accordingly, there is a need to overcome the deficiencies as described herein above.